Nucleate pool boiling heat transfer of acetone and HFE7200 on copper surfaces with nanoparticle coatings

• Nucleate pool boiling performance of two well-wetting liquids, i.e., acetone and HFE7200, on three nanoparticle-coatedsurfaces were experimentally studied and compared with that of the smoothsurface. Electrophoretic deposition was used to fabricate nano-porous surfaces.Surface roughness, static and advancing contact angles, capillarity of the smoothand coated surfaces were characterized. Compared to the smooth surface, thenanoparticle-coated surfaces decreased the wall superheat by more than 50% foracetone and 65% for HFE7200 at the same heat flux level, and accordinglyenhanced the heat transfer coefficient by up to 85% for acetone and up to 200%for HFE7200. Bubble departure diameters were measured and correlated with theadvancing contact angle, the capillary length and the Jacob number. A newmechanistic heat transfer model was proposed based on the heat flux partitionmethod. The advancing contact angle was suggested to be used for calculation ofthe active nucleation site density. Based on the mechanistic model, transientheat conduction on and around nucleation sites over the whole bubble cyclecontributes the most (>70%) to the total heat flux, while microlayerevaporation contributes around 10-30% to the total heat flux, with negligiblenatural convection. The critical heat flux was not enhanced for the twowell-wetting liquids.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Energiteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Energy Engineering (hsv//eng)

Nyckelord

pool boiling

heat transfer coefficient

nanoparticle

electrophoretic deposition

critical heat flux

heat transfer modelling

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